In the building of a tire on a single-stage tire building machine, a cylindrical carcass is formed by applying one or more plies of tire fabric to a tire building drum. Tire beads thereafter are positioned in proper relation to the cylindrical carcass and properly locked in place, such as by radially expandable bead locks located at each end of the drum, for subsequent wrapping of the tire components thereabout. For final application of tire components, such as a belt and tread assembly, the cylindrical carcass is expanded or converted to toroidal or tire shape. As the tire is converted, the bead locks move uniformly toward each other.
During the aforementioned formation of the cylindrical carcass, the fabric plies desirably are firmly stitched together as they are applied to the drum. Further, particularly when constructing larger and more complex tires, it is desirable to apply other tire components such as chafers, body plies, or belt cushions, which also desirably should be firmly stitched. To obtain firm stitching of tire components, there should be a center deck between the bead locks which is substantially rigid throughout its axial length, of substantially uniform diameter, and yet which will axially contract or collaspse as the tire is brought or converted to its toroidal shape. For the construction of large tires, the distance between the initial bead placement and the final bead position in tire shape can be substantial.
Tire building machines which include an axially contractible and expandable center deck have been employed in tire construction. Some known axially contractible center decks employ an inflatable membrane, such as seen in Eicholz et al U.S. Pat. No. 4,011,127. While readily contractible during conversion of the tire to its toroidal shape, such membranes alone lack the desired rigidity to allow rapid and firm stitching to adhere the tire components to one another.
Other known axially contractible center decks have interfitting rigid parts or segments, such as seen in Benns U.S. Patent 3,526,561. However, such decks when expanded have gaps or spaces between the interfitting rigid deck parts or segments. Accordingly, such decks do not provide a rigid, axially continuous support for the tire components. As seen in the Benns patent, an elastic sleeve may surround the interfitting rigid deck segments. Of course, this still does not provide a rigid, axially continuous support for the tire components in that the elastic sleeve is not rigidly supported in the regions overlying the gaps. For another patent showing an axially contractible center deck employing interfitting rigid parts or fingers, reference may be had to Enders U.S. Pat. No. 4,214,939.
Another problem with some center decks employing rigid parts or segments is that they require complicated mechanisms for expanding and contracting the deck, and further some are capable of providing a generally cylindrical deck surface for tire component application only when in its fully expanded position. Such decks are expensive to manufacture, difficult to maintain, and/or require replacement of the deck segments or parts, or adjustment thereof, when making tires of different widths or bead sets. Examples of center decks having one or more of these deficiencies can be seen in Leblond U.S. Pat. No. 3,718,520 and Appleby et al U.S. Pat. No. 3,784,437.
Some known decks, however, do remain generally cylindrical as they are axially expanded and contracted, such as seen in Woodhall et al U.S. Pat. No. 3,698,987 and the aforementioned Benns patent. However, such decks can at best be expanded twice their fully contracted or collapsed lengths without additional gaps occurring between the relatively axially moving parts or segments thereof. Accordingly, the range of axial working lengths for any given diameter deck is limited.